Batch dishwashers are dishwashers which can be manually loaded and unloaded. Batch dishwashers (also called “box-type warewashers”) may be hood-type dishwashers (“hood-type warewashers”) or front-loader dishwashers (“front-loader warewashers”). Front-loader dishwashers may be under-counter machines, top-counter machines or free-standing front-loader dishwashers.
A dishwasher which is in the form of a batch dishwasher usually has one treatment chamber for cleaning washware. The treatment chamber generally has arranged beneath it a wash tank in which liquid from the treatment chamber can flow back due to the force of gravity. The wash tank contains wash liquid which is usually water to which detergent may be added if required.
A dishwasher which is designed as a batch dishwasher usually also has a wash system comprising a wash pump, a line system which is connected to the wash pump, and comprising a large number of spray nozzles which are formed in at least one wash arm. The wash liquid contained in the wash tank can be conveyed from the wash pump to the wash nozzles via the line system and can be sprayed onto the washware to be cleaned through the wash nozzles in the treatment chamber. The sprayed wash liquid then flows back into the wash tank.
A dishwasher of this kind which is designed as a batch dishwasher is known, for example, from document DE 10 2005 023 429 A1.
The term “washware” used in the present document is intended to be understood to mean, in particular, crockery, glasses, cutlery, cooking utensils, baking utensils and serving trays.
The invention in particular relates to a dishwasher in the form of a commercial utensil washer or dishwasher which is designed as a batch dishwasher and is realized as a hood-type dishwasher, wherein the dishwasher has a treatment chamber with at least one wash system which is designed as a recirculation system.
Dishwashers of this type are used primarily (but not exclusively) in relatively small sculleries, for example in relatively small canteens, in particular school canteens, or in the catering sector. The use of dishwashers of this kind is characterized by said dishwashers being used in sculleries in which there is generally only a limited amount of floor space available.
A commercial dishwasher, in particular a hood-type dishwasher, which is designed as a batch dishwasher differs from a domestic dishwasher in particular in that a commercial dishwasher has to be designed in such a way that—depending on the treatment program selected—program run times of between one and five minutes can be realized, whereas domestic dishwashers generally have run times of up to 2.5 hours or more. On account of the short program duration required in commercial dishwashers, techniques employed in domestic dishwashers generally cannot be readily transferred to commercial dishwashers.
Commercial dishwashers which are in the form of batch dishwashers normally operate in two main process steps: a first step which includes washing with a wash liquid, and a second step which includes final rinsing with heated fresh water with the metered addition of a final rinse aid.
In order to be able to carry out these process steps, a commercial dishwasher, which is designed as a batch dishwasher, is generally equipped with two independent liquid systems. One liquid system is a wash water circuit which is responsible for washing the washware, with washing being carried out using recirculated water from the wash tank of the dishwasher. The other liquid system is a fresh water system which is responsible for final rinsing. Final rinsing is carried out using fresh water, preferably using fresh water from a water heater (boiler). The fresh water is likewise collected by the wash tank of the dishwasher after being sprayed.
The main objective of final rinsing is to remove wash liquor from the washware. In addition, the final rinse water which flows into the wash tank during the final rinse step serves to regenerate the wash water which is present in the wash tank.
Before fresh water is sprayed as final rinse liquid as a result of final rinsing and thus conducted into the wash tank of the dishwasher, a quantity of wash liquid which is equal to the quantity of fresh water is pumped out of the wash tank.
Commercial dishwashers which are designed as batch dishwashers are usually equipped with several programs. These programs differ mainly due to program run times of the wash process of different lengths. The operator has the option of selecting a short wash program for washware which is lightly soiled, or of selecting a correspondingly longer wash program for washware which is heavily soiled.
Commercial dishwashers, which are designed as batch dishwashers and are designed for loading washware into and unloading washware from the treatment chamber in batches, are, in particular, front-loader machines or hood-type machines. In the case of front-loader machines, the washware is placed in a rack and the rack which is loaded with washware is placed in the treatment chamber of the dishwasher through a front door and, after cleaning, is removed again through the front door. In the case of hood-type machines, the dish racks which are loaded with washware are pushed manually into the treatment chamber from an entry end and manually removed from the treatment chamber from an exit end when a wash program is complete. Front-loader machines and hood-type machines contain only a single treatment chamber for treating the washware. The front-loader machines may be under-counter machines or top-counter machines.
Virtually without exception, commercial dishwashers which are designed as batch dishwashers and are designed for loading washware into and unloading washware from the treatment chamber in batches are realized with entry and/or exit tables. The dirty washware is usually manually pre-cleared and manually pre-washed at the entry end of the dishwasher. Furthermore, the dirty washware is loaded into special dish racks here. The exit end is used for drying purposes and unloading the dish racks.
Particularly in the case of dishwashers which are realized as hood-type machines, the wash level is usually at the same height as the entry and exit tables. In this way, the dish racks which are to be cleaned can be easily and ergonomically pushed into the dishwasher from the entry table and, after cleaning is complete, pushed out of the dishwasher onto the exit table.
The term “dishwashing level” used in the present document is intended to be understood to mean the horizontal level at which the dish rack is situated. In the treatment chamber of a dishwasher, the dishwashing level is generally defined by a guide system, in particular guide rails, which accommodates a dish rack which is pushed into the treatment chamber from an entry table which is provided at the inlet end of the machine.
Commercial batch dishwashers, in particular those which are realized as hood-type dishwashers, are designed to clean large quantities of washware in as short a time as possible. For example, in state-of-the-art hood-type dishwashers, the duration of a preset standard program, which is usually used for washware, such as plates, trays, cups and glasses, with a normal level of soiling, lasts only approximately 60 to 80 seconds. This provides a theoretical capacity of up to 45 to 60 racks per hour.
However, depending on the washware and the degree of soiling of said washware, it may be necessary to select a treatment program with a longer duration in order to ensure a satisfactory cleaning result.
For example, in this connection, it is known from the prior art that commercial batch dishwashers have, for example, a special cutlery treatment program (intensive treatment program) for improving the cleaning result specifically of cutlery. An intensive treatment program of this kind lasts considerably longer than said 60 to 80 seconds of the standard treatment program, for example approximately 360 seconds. Therefore, it is clear that the capacity of the machine when the intensive treatment program is chosen is greatly reduced since the treatment chamber is occupied for considerably longer than would be the case with a standard treatment program.
In practice, this leads to special treatment programs which are usually already provided as alternatives to the standard treatment program as standard generally being chosen only rarely by the operator of the dishwasher, in spite of the improved washing performance, since the corresponding program duration is found to be too long, in particular at peak times, that is to say when there is an increased amount of washware arriving. Instead, the heavily soiled washware (in particular cutlery and GN containers) is often likewise treated using the standard treatment program and the poor washing performance is compensated for by additional manual operating steps, such as manual pre-washing of heavily soiled GN containers or separate pre-soaking of cutlery for example.
With heavily soiled washware, as is often the case with pots or pans for example, it is necessary in particular to correspondingly increase the cycle length in order to be able to achieve an acceptable cleaning result. In the case of hood-type dishwashers, the program run times are usually extended to up to 10 minutes in order to be able to clean heavily soiled washware, in particular pots and pans with burnt-on food residues, in a hygienically satisfactory manner.
Consequently, the dishwasher cannot be used to clean lightly soiled washware, such as plates, cups, cutlery or glasses for example, during these extended cycle times. In other words, the dishwasher is blocked for a relatively long period of time in order to clean heavily soiled washware, in particular pans and pots, this often leading to problems in relatively small sculleries since accruing dirty dishes cannot be cleaned or further processed during this period of time.
Therefore, in practice, particularly during peak times, the dishwasher is used only to clean lightly soiled washware, such as plates, cups and glasses for example, while the heavily soiled washware (in particular pots and pans) are manually cleaned in order to prevent the dishwasher being blocked for too long due to the relatively long cycle times required.